Chromium–saponite clay catalysts: Preparation, characterization and catalytic performance in propene oxidation

Abstract

Chromium-saponite catalysts have been prepared by two synthesis procedures. The first method consisted in the intercalation of the saponite with solutions containing aluminium and chromium oligomers with various molar ratios, while the second one consisted in the incipient wetness impregnation of alumina-pillared saponite with several chromium salts, ammonium chromate, Cr(II) acetate and Cr(III) nitrate. Several techniques, X-ray diffraction, nitrogen physisorption at À196 8C, thermogravimetric and differential thermal analysis, infrared and DR-UV-vis spectroscopies, temperature-programmed reduction and electron paramagnetic resonance spectroscopy at À196 8C, have been used to characterize and to compare the properties of the materials synthesized. The results show that the solids obtained combine the layered structure of the clay and the thermal stability given by the alumina pillars. The catalysts have been tested in the oxidation of propene, showing a catalytic behaviour according to the Mars-van Krevelen mechanism, the performance not depending on the method in which chromium was incorporated to the clay.

Synthesis and characterization of Cr-pillared clays: modelling using factorial design methodology

“…Thus, chromium(III)-pillared interlayered clays (Cr-PILCs) are recognized as potential catalysts in conversion of hydrocarbons [11], hydrocracking of heavy liquid fuels [12,18], propene oxidation [24] and oxidation of chlorinated hydrocarbons [25].…”

Acetalation of Pentaerithritol Catalyzed by an Al-Pillared Saponite

“…Characterization by thermogravimetry, differential thermal analysis, FT-infrared spectroscopy, etc. [34], -not shown for simplicity-, shows that all the properties of the catalyst are typical for pillared saponite.…”

“…The raw material was previously purified by dispersion-decantation, obtaining the 2 lm fraction [34].…”

“…In fact, Al-pillared Yunclillos-Cabañas saponite has already been used in some previous works [34]; in which more information about this clay can be found. The essential characterization data on the catalyst synthesized for the present work are reported here.…”

Ni/Pillared Clays as Catalysts for the Selective Catalytic Reduction of Nitrogen Oxides by Propene

“…So far, the most common De-NO x catalysts employed are based on transition and noble metals supported over zeolites or alumina [11][12][13]. The use of metal pillared clays in this reaction has not been extended, a few reports based on Fe-, Co-, Cr-, Ti-and CuPILCs [14][15][16][17][18], and more recently noble metal PILCs having been published [19]. We have focused our attention both on pillared clays, as optimum microporous materials for this reaction, and on Ni-catalysts, described in the literature as effective for NO x reduction in presence of C 2 and C 3 hydrocarbons [20,21].…”